1. Field of the Invention
The present invention relates to a hand-held power tool such as, e.g., a screw driving tool or the like, and including a housing, a motor-driven shaft for driving a working tool and extending in the housing, and a torque cut-off device for presetting a torque of the driving shaft and having a rotatable control sleeve with a control cam and a control element secured in the housing without a possibility of rotation but with a possibility of an axial displacement relative to a rotational axis of the control sleeve and cooperating with the control sleeve for presetting the torque of the drive shaft.
2. Description of the Prior Art
Hand-held power tools and, in particular, screw driving tools, of the type described above are usually provided with torque cut-off means in order to prevent, e.g., a motor for driving the tool from overload or a screw from being damaged. The torque cut-off means generally includes a control device for presetting the torque. For its actuation, the control device is provided with a rotatable control sleeve having a control cam. The control device is also used for actuation and deactuation of a percussion mechanism and the like. A screw driving tool is provided, e.g., with a ratchet clutch the engagement position of which is insured by a spring acting in the axial direction of the clutch.
Generally, hand-held power tools, in particular screw driving tools having a housing and a torque cut-off device are known. The torque cut-off device has, for presetting a torque of a motor-driven shaft for driving a working tool, a control device including a control sleeve. The control sleeve has a control cam probed by a control element that is secured in the housing without a possibility of rotation but with a possibility of axial displacement with respect to the rotational axis of the control sleeve for presetting the torque. In order to insure a precise and stable position of the control sleeve on the housing, the control element has at least two probing sections which contact the control cam and are uniformly arranged over the circumference of the control cam.
The drawback of the device discussed above consists in that the two probing sections do not insure a precise presetting of a torque as the control sleeve, which cooperates with the two probing sections, rotates maximum by 180°. With the use of more than two probing sections, the angular region of rotation of the control sleeve is correspondingly reduced.
Accordingly, an object of the present invention is to provide a torque cut-off device that can be economically manufactured and, at the same time, would insure a precise and minute presetting of a torque.